In a key environmental decision affecting the Minntac iron ore mine near Mountain Iron, Minn., the Minnesota Department of Natural Resources ruled Thursday that the mine can be expanded without having to obtain a new environmental impact statement, which could cost from $1 million to $3 million.

U.S. Steel has proposed a 483-acre extension of the Minntac facility, which employs 1,400 workers. The changes are designed to extend the life of the mine by about 16 years without increasing the mine's rate of production or annual production volume.

The DNR ruled that an environmental impact statement wasn't needed for the expansion because the environment would be protected by the plant's current water quality permit and a new permit likely to be granted soon. It also said the environment was protected as a result of mine oversight by other regulatory agencies including the Minnesota Pollution Control Agency, and the U.S. Army Corps of Engineers.

But the Minnesota Center for Environmental Advocacy, a nonprofit organization, insisted that a new environmental impact study was needed to update the Minntac plant's 1987 water quality permit. The aging permit provides inadequate protection from pollutants such as heavy metals and sulfates that are better understood today, said Kathryn Hoffman, a staff attorney for the center, based in St. Paul.

"The Minntac mine has a lot of problems," Hoffman said. "The DNR has not identified adequate measures to prevent pollution at the mine site, and if they can't find mitigating measures they need to do an environmental impact statement."

The DNR's Steve Colvin disagreed.

"If they're arguing that the existing permit for the mine needs to be updated, that's about the existing mining project," said Colvin, DNR deputy director of the ecological and water resources division in St. Paul. The DNR's ruling was about the expansion, not the existing mine, he said.

Colvin said he knew the DNR decision would get a lot of attention.

"We received over 200 public comments on this project, which is more than you usually get for project of this type," Colvin said. "Many of those people wanted us to do an environmental impact statement."

A spokeswoman for Minntac owner U.S. Steel in Pittsburgh declined to comment on the DNR's ruling.

Steve Alexander • 612-673-4553